Search results

Search Forums New Posts
  1. dorke

    Green LED power consumption

    Something doesn't compute: With a 1.2K resistor that red led current is: (3.7-1.9)/1.2k=1.5ma much less than the led 20ma "advertised current" To your questions: With the same resistor, the higher the led Vf ,the lower the led current(= battery current). The time the battery will be...
  2. dorke

    Can i Erase last digit on the LCD screen? *I am a total newbie*

    Simplest solution, non destructive and reversible: Put a sticker on it...;)
  3. dorke

    Green LED power consumption

    You can calculate it very simply. Since you haven't noted the resistor value(assuming there is one). and assuming the original red led is driven at 20ma with a lithium battery voltage of 3.7V we get: R=(3.7-1.9)/20ma=90 ohm With the smae resistor for the green led we get...
  4. dorke

    GY512 Diode

    A much clearer photo is needed. No writing on the diode?
  5. dorke

    Replacing A5sHB transistor (netbook)

    This is hard to follow. are you getting a 5v on the usb port? what do you measure on Q4 pins? What voltage do you get between pins 8 and 4 of the 25x40 -windbond IC, (near the VIA IC)? In the top photo you have a bunch of dc-dc converters that should create the different dc voltages for the...
  6. dorke

    digital clock

    What is your purpose of building the clock? Educational(self?) only? A clock for "daily use"? Other? Size requirements? Mains operated or battery? Alarm,snooze etc.? There are so many ways to go about this, most are not economical since you can buy such a clock for nearly nothing these days
  7. dorke

    Scope calibration

    In this case .you should buy professional equipment. It calls for a deeper study of the calibration equipment needed for now days test instruments, and do it wisely since they are mucho-dinero;) That HP1740 is almost a museum item.
  8. dorke

    Fluke 89iv funny reading

    Your meter is fine! Don't even open it or touch anything, just use it as it is. As mentioned above a few times, your are measuring the test leads resistance and a reading of 0.13 ohm is normal.
  9. dorke

    Replacing A5sHB transistor (netbook)

    The photos are not clear enough to read most parts.
  10. dorke

    Replacing A5sHB transistor (netbook)

    O.k I'm re-posting from #7: Please post two separate and clear(so that the device markings are readable) photos of the two squared areas in green and pink.
  11. dorke

    Scope calibration

    This calibrator is a professional tool. I wouldn't buy it unless you are in the business of fixing test equipment like scopes,frequency counters etc. In this case, I think it is more expansive than the scope you are trying to fix... and it is absolutely not needed,there are many other ways to...
  12. dorke

    Replacing A5sHB transistor (netbook)

    If you connect a fully charged battery alone without the adapter. what is the voltage you measure on the battery terminals? and along the battery related traces pink-line and green-line?
  13. dorke

    Frequency divider (less than 1MHz)

    Well , here is a slight modification that can work. We don't need to get into square to sine wave convertion if we take the output of the VCO("sine by nature") to be our sine wave itself... The input analog filters with a BP of 9khz and the lock-in of the PLLs with a quarter of that at about...
  14. dorke

    Frequency divider (less than 1MHz)

    Hop,yes I know that reply was to your post #19 :asking for separate f1 and f2 on BNCs ;) And I did offer the triangular to sine convertion on #8;) While I was writing the above post you posted yours last one, We do think alike here...
  15. dorke

    Frequency divider (less than 1MHz)

    I was thinking that a separation of the two signals f1 and f2 shouldn't be a difficult task . Here is a way to go with: the Q of the band-pass filters is realizable about 20. and the lock-in and capture of the PLLs is set by the loop-filter.
  16. dorke

    Kinetic Phone Charger

    It is most likely that the charging current of the "super caps" is large , so that the "generator" is overloaded and it's voltage drop's. i.e your generator has very low power capabilities Try using a "lighter load" instead of the "caps", like a 5k to 10k (variable) resistor to verify this.
  17. dorke

    Gate driver datasheet for IGBT

    P.S About the input and output capacitors to the LM317L. since the device is drawing very little average current(max 3mA): The input filter capacitor can be relatively small, I think a single 100uF-electrolyt (or smaller )is enough. The output capacitor should be 1uF-tantalum (maybe a bit...
  18. dorke

    Gate driver datasheet for IGBT

    Yes, for the LM317 it is always 1.25V typical value. But for other devices you should (always) consult the datasheet .
  19. dorke

    Scope calibration

    O.K Do you have the service manual of the HP1740A?
  20. dorke

    Replacing A5sHB transistor (netbook)

    Before we continue,a few questions: 1.What is the rated battery voltage and current and type? 2.Is it the "original one"? 3.How many contacts those it have? 4.A clear photo of the battery please. 5.Is the adapter the original one? 6.Anything written on the adapter socket on the netbook?
Top